This invention relates to a cylinder head fastening structure for an internal combustion engine and more particularly to an improved engine layout for an overhead cam shaft engine that facilitates servicing.
As is well known, the cylinder head of an engine is normally fixed to the cylinder block either by means of bolts or by means of studs and nuts. When the engine embodies one or more overhead cam shafts, the relative positioning between the cam shafts and the head fasters often results in compromise of the placement of either or both. For example, it is desirable to position the overhead cam shaft directly above the cylinder bore so that the valves can be located relative to the cylinder so as to insure good volumetric efficiency and breathing. However, it is also desirable to locate the cylinder head fastener in the same location. When both the cam shaft and cylinder head fastener are so located, servicing has been a problem with the prior art type of constructions. That is, retorqueing of the cylinder heads after a rebuild will necessitate removal of the cam shafts. To avoid these problems, it has been proposed to offset the cam shafts from a position over the cylinder bores, thus resulting in a less than optimum placement. The problem is particularly acute when two overhead cam shafts are employed. It is desirable to position the cam shafts as close as possible to each other to insure good valve placement in the cylinder and also so as to reduce the necessity for using interconnecting motion transmitting mechanism between the cam lobes and the valve stems. With prior art fastening arrangements, however, such close position has been impossible unless serviceability is sacrificed.
It is, therefore, a principal object of this invention to provide an improved fastening arrangement for the cylinder head of an internal combustion engine.
It is a further object of the invention to provide an improved cam shaft and cylinder head fastening arrangement for an overhead cam shaft engine.